Material treatment ovens are employed to heat elongated moving workpieces such as carbonaceous fibers, adhesive coated webs and coated wires from which solvent or other by-products of the heating process are to be removed. These ovens commonly make use of an elongated heating cavity or chamber, and may contain payout and take up rollers at opposite ends of the cavity to feed material into the cavity and to collect the material as it exits from the cavity. In the usual course, air or other gas is heated by electric or gas heaters and is directed into the oven cavity where it contacts and heats the moving workpiece. The hot air collects solvents or other products of the heating process from the workpiece, and eventually is exhausted. The exhausted hot air, laden with the by-products of the heating process, may then be subjected to solvent recovery or other pollution controlling processes to prevent the solvent or other by-products from escaping into the atmosphere. It is generally impractical to reuse the hot air that is exhausted from the oven cavity. As a result, great quantities of fresh air must be heated and although a portion of the heat may be recovered, the energy loss can be large. Moreover, since necessarily a large volume of heated air passes through the oven cavity to both heat the material and to receive solvent or other chemicals from the material being heated, high volume solvent recovery or other air cleansing units may also be required.
Another type of oven utilizes a cavity in which heat radiators are positioned to radiate heat energy toward a workpiece. Since the temperature of the workpiece depends upon the amount of radiant heat that it absorbs, it is often difficult to control with accuracy the temperature to which the workpiece is heated. It is also difficult to control with accuracy the temperature of the radiant elements. Care must be taken to avoid dangerous concentrations of solvent or other volatile materials in the oven cavity. Oven cavities employing radiant elements commonly either are largely open or are quite short to avoid build up of dangerous concentrations of solvents or other impurities, or, if longer, are employed with workpieces which yield little, if any, volatile or air-entrained products of the heating treatment.